The field of the present invention relates to data reading devices such as for example bar code scanning systems.
In data reading devices, a return light signal from the object or symbol being read is focused onto a detector or detector array. In the example of a bar code scanner reading the bars and spaces of a typical bar code, there needs to be sufficient difference in signal intensity between the signal corresponding to the light space and the signal corresponding to the dark bar in order for the processor to differentiate therebetween. In scanner applications there has been demand for increased depth of field, i.e., the range of distance over which the scanner can effectively scan.
There are several methods for improving depth of field, but there are essentially two areas which may be controlled, namely (1) outgoing beam generation and (2) collection. This application focuses on methods for improving depth of field and signal differentiation from the collection side.